1. Field of the Invention
The present disclosure relates to a key module and a keyboard having the same; in particular, to a key module which evenly supports a keycap while preventing tilting of the keycap and is suitable for slim keyboards, and a slim keyboard having the same.
2. Description of Related Art
The demand for slim computers (e.g. laptops) calls for keyboards using scissor-type structures which guides the up and down movement of the keycaps and balances the force applied by the user on each key. As shown in FIG. 1, the keycap 10 of a conventional key structure 1 has a first sliding joint 101 and a first pivot joint 102. The base 20 has a second sliding joint 201 and a second pivot joint 202. Scissor structure 30 (scissor switch) includes a first support unit 301 and a second support unit 302. The first support unit 301 is pivotally connected to the second support structure 302. The first support structure 301 has a first sliding portion 303 and a first pivot shaft 304. The second support unit 302 has a second sliding portion 305 and a second pivot shaft 306. The first sliding portion 303 can be slidably disposed in the first sliding joint 101, and the first pivot shaft 304 can rotatably pivot about the second pivot joint 202. The second sliding portion 305 can be slidably disposed in the second sliding joint 201, and the second pivot shaft 306 can rotatably pivot about the first pivot joint 102. In other words, the keycap 10 has a fixed end E1 (corresponding to the side of the scissor structure 30 having the first pivot shaft 304 and the second pivot shaft 306) and a sliding end E2 (corresponding to the side of the scissor structure 30 having the first sliding portion 303 and the second sliding portion 305.
As shown in FIG. 1A, when the sliding end E2 of the keycap 10 is pressed, the sliding end E2 moves an ineffective transverse distance along the first sliding joint 101 (as shown by arrow M11) and an ineffective vertical distance toward the base 20 (as shown by arrow M12), after which the sliding end E2 moves in conjunction with the scissor structure 30 toward the base 20 in an effective vertical stroke for pressing an elastic body 4. Hence, when the keycap 10 is pressed on one side, the sliding end E2 moves an ineffective distance before moving downward in conjunction with the scissor structure 30, therefore producing an undesired tilting of the sliding end E2 and flipping of the keycap 10. The transverse movement reduces the effective vertical travel distance of the key structure, such that the requirement of small thickness is not met for slim or super slim keyboards. Additionally, given that the force applied on the keycap 10 is not evenly distributed across the entire keycap 10, the key structure easily becomes tilted and unstable, even unable to complete the motion for driving the scissor structure 30, such that the switch cannot be triggered and more noise is created during operation. Moreover, when the conventional key structure 1 is applied on super slim keyboards, given that the ineffective distance of the sliding end E2 of the keycap 10 is overly long, the effective vertical travel distance is insufficient. As a result, electrical conduction is poor and undesirable tilting of corners of the keycap 10 is more serious, rendering the key structure 1 less suitable for super slim keyboards.
Additionally, the current method of assembling keycaps 10 onto scissor structures 30 requires human labor at least two steps. First, the sliding joint 101 of the keycap 10 must couple to the first sliding portion 303 of the scissor structure 30 from a slanted position. Then, the first pivot joint 102 of the keycap 10 must be coupled to the second pivot shaft 306 of the scissor structure 30. As can be seen, using human labor for assembly not only compromises the speed of assembly but also increases the rate of poor assemblies. Additionally, the force of assembly is not easily controlled, which leads to damages to the keycap 10 or the scissor structure 30. Therefore, the assembly of the keycap 10 and the scissor structure 30 requiring human labor cannot be automated and the production speed cannot be increased.
Additionally, as shown in FIG. 2, when the conventional key structure 1 is applied on longer or irregularly shaped keys (e.g. Space, Shift, Backspace and Enter), the unstable scissor structure 30 and the easily tilted keycap 10 lead to lack of rigidity of the key structure 1. Therefore, metal stabilizer links 40 span the majority of the region of the keycap 10 to independently connect to the keycap 10 and the base 20, for increasing the stability of the keycap 10 during up and down motion, and additional metal stabilizer links 40 are disposed at the peripheries of the scissor structures 30 for solving the problem of tilting and instability of the key structure 1. As shown in FIG. 2, five metal stabilizer links 40 are used. Given that the metal stabilizer links 40 and the scissor structures 30 are very close to each other, assembly of the key caps 10 of the key structure 1 is more difficult. Moreover, given the same size of the keycap 10, the conventional scissor structure 30 must be smaller in order to free up sufficient space to accommodate metal stabilizer links 40, exacerbating the problem of insufficient rigidity of the scissor structure 30 and the margin of error during production. Additionally, additional metal stabilizer links 40 not only creates serious noise during operation, but also complicates assembly, and increases the rate of poor quality and cost of human labor.